143 lines
6.3 KiB
HTML
143 lines
6.3 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="abstract" content="If you want to keep duplicates in the result of a UNION, specify UNION ALL instead of just UNION." />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Specify UNION ALL</title>
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</head>
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<body id="rbafykeyuall"><a name="rbafykeyuall"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Specify UNION ALL</h1>
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<div><p>If you want to keep duplicates in the result of a UNION, specify
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UNION ALL instead of just UNION.</p>
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<div class="section"><p>Using the same as steps and example as UNION:</p>
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</div>
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<div class="section"><p>Step 3. SQL combines two interim result tables:</p>
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<pre><strong>SELECT</strong> EMPNO
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<strong>FROM</strong> CORPDATA.EMPLOYEE
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<strong>WHERE</strong> WORKDEPT = 'D11'
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<strong>UNION ALL</strong>
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<strong>SELECT</strong> EMPNO
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<strong>FROM</strong> CORPDATA.EMPPROJACT
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<strong>WHERE</strong> PROJNO='MA2112' <strong>OR</strong>
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PROJNO= 'MA2113' <strong>OR</strong>
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PROJNO= 'AD3111'
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<strong>ORDER BY</strong> EMPNO</pre>
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<p>Resulting in an ordered result table
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that includes duplicates:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="hsides" border="1" rules="all"><thead align="left"><tr valign="top"><th valign="top" id="d0e71">EMPNO</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e71 ">000060</td>
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</tr>
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<tr><td valign="top" headers="d0e71 ">000150</td>
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</tr>
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<tr><td valign="top" headers="d0e71 ">000150</td>
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</tr>
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<tr><td valign="top" headers="d0e71 ">000150</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000160</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000160</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000180</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000180</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000190</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000190</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000190</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000200</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000210</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000210</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000210</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000220</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000230</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000230</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000230</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000230</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000230</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000240</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">000240</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">200170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e71 ">200220</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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<div class="section"><p>The UNION ALL operation is associative, for example:</p>
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<pre>(<strong>SELECT</strong> PROJNO <strong>FROM</strong> CORPDATA.PROJECT
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<strong>UNION ALL
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SELECT</strong> PROJNO <strong>FROM</strong> CORPDATA.PROJECT)
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<strong>UNION ALL
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SELECT</strong> PROJNO <strong>FROM</strong> CORPDATA.EMPPROJACT</pre>
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</div>
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<div class="section"><p>This statement can also be written as:</p>
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<pre><strong>SELECT</strong> PROJNO <strong>FROM</strong> CORPDATA.PROJECT
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<strong>UNION ALL
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(SELECT</strong> PROJNO <strong>FROM</strong> CORPDATA.PROJECT
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<strong>UNION ALL
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SELECT</strong> PROJNO <strong>FROM</strong> CORPDATA.EMPPROJACT)</pre>
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</div>
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<div class="section"><p>When you include the UNION ALL in the same SQL statement as a
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UNION operator, however, the result of the operation depends on the order
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of evaluation. Where there are no parentheses, evaluation is from left to
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right. Where parentheses are included, the parenthesized subselect is evaluated
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first, followed, from left to right, by the other parts of the statement.</p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbafykeyu.htm" title="Using the UNION keyword, you can combine two or more subselects to form a fullselect.">Use UNION keyword to combine subselects</a></div>
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</div>
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</div>
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</body>
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</html>
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